Borderline personality disorder (BPD) is a severe disorder in which individuals often engage in extreme behaviors such as self-injury, impulsive behaviors, substance abuse and suicidal behavior. Individuals with BPD symptoms utilize the health care system (e.g., visits to physicians, emergeny rooms, and hosptializations) at alarmingly high rates (Hueston, Mainous, &Schilling, 1996) and are at extremely high risk for death by suicide. This makes BPD a significant pulic health concern. Although successful treatments have been developed for BPD (Dialectical Behavior Therapy;Linehan, 1993), little attention has been given to understanding the underlying causes and functional aspects of the maladaptive behaviors seen in BPD, valuble information for the treatment of this disorder. Linehan's (1993) theoretical model of BPD asserts that individuals with BPD have significant problems with emotion dysregulation in that they 1) have a heightened sensitivity to emotional stimuli, 2) experience emotions as extremely intense, and 3) they have a slow return to emotional baseline. Research also suggests that the maladaptive behaviors of individuals with BPD may serve the common purpose of emotion regulation. Recent findings in the field of emotion science provide evidence that rumination (a form of cognitive emotion dysregulation) may account for the emotion dysregulation seen in BPD. Rumination is defined as focusing attention and thoughts on the causes and consequences of emotionally relevant stimuli. Consequently, rumination has been shown to magnify and perpetuate negative affect;intense negative affect, in turn, may result in increased attention to emotionally relevant stimuli - potentially resulting in a cycle that causes a "cascade" of intense emotions (Selby et al., in press). The proposed studies will examine the role of cognitive emotion dysregulation (defined as high levels of rumination) in BPD, as well as examine the role that maladaptive behaviors (including suicidal behaviors) have in interfering with rumination. Study 1 will examine the role of rumination in BPD with an induced rumination on negative affect procedure. A subsequent pain tolerance test with a cold-pressor will provide a proxy for self-injury, and information about the distracting quality of pain. The second study will examine the contextual and ruminative features surrounding behavioral dysregulation in BPD with an Ecological Momentary Assessment protocol. PUBLIC HEALTH RELEVANCE: This study will examine if real-time rumination and interpersonal problems tend to precede behavioral dysregulation in the daily life of BPD individuals, through the use of palm pilots. This study will also specifically examine if an interaction between rumination and interpersonal problems is associated with NSSI in individuals with BPD.